In certain prior art, a monitoring system monitors the isolation or electrical resistance between a terminal and electrical ground by a test switch switching a known resistance value (e.g., high resistance to limit current) between the electrical terminal and electrical ground to measure voltage across or current through the known resistance value. For example, the electrical terminal may represent a positive direct current terminal or a negative direct current terminal of a tested device, where the electrical terminal is not directly connected to electrical ground or chassis ground. In some prior art, a first test switch is placed in series with a first test resistor and a second test switch is placed in series with a second test resistor, where the first switch and the second switch are sequentially activated to test isolation between a first terminal (e.g., positive direct current terminal) and ground and isolation between a second terminal (e.g., negative direct current terminal) and ground. However, if the first switch or the second switch fails in a shorted state, the leakage resistance between one electrical terminal and electrical ground will appear to be low, providing a false positive of a lack of isolation or improper leakage resistance in the tested device. Accordingly, there is need for a method and system for monitoring electrical isolation that can differentiate between a truly low leakage resistance or determine whether there is a fault in the test circuit.